JP7425687B2 - Power system stabilization system - Google Patents

Description

Embodiments of the present invention relate to a power system stabilization system that maintains synchronization stability of generators by restricting power supply when an accident occurs in the power system.

Traditionally, system out-of-step/accident prevention relays have been used to prevent generator out-of-sync phenomena (generators becoming out of synchronization and resulting in unstable operation) and to maintain synchronization stability in the power system. Techniques related to systems (hereinafter referred to as power system stabilization systems) have been disclosed (for example, Non-Patent Document 1).

The online pre-calculation type power system stabilization system disclosed in Non-Patent Document 1 uses grid information obtained online (including, for example, the connection state and supply and demand state of the power system) to calculate assumed accidents that are set in advance. Transient stability calculations are performed for each hypothetical accident, control details are determined for each hypothetical accident, and a control table is set based on the determination results. When an accident actually occurs, the power system stabilization system performs control by comparing the accident type with a control table.

Note that the control content is the generator that is disconnected in the event of an accident. "Disconnecting" means disconnecting from the power grid, and hereinafter may be expressed as "shutdown" or "electrification." In addition, control for forcibly shutting off some generators from the power system in order to prevent the effects of an accident from spreading to the entire power system is called power supply restriction or electricity control. In the following description, a control target such as a generator selected as a power restriction target is referred to as a power restriction target, and a process for determining a power restriction target is referred to as power restriction target selection. Note that the control content may include, in addition to power supply restriction, turbine early valve actuation (EVA) that suppresses acceleration of the generator. In addition, the target of electrical blackouts is not limited to synchronous generators (hereinafter referred to as synchronous generators) such as thermal power generators and nuclear power generators that are synchronously connected to the power grid, but also direct current power generated by solar panels (PCS). Solar power generation that is converted into AC power by a conditioning subsystem and supplied to the power grid, and wind power that is converted from AC power generated by a wind generator to DC power by a converter and then converted back to AC power and supplied to the power grid. Power sources that are not synchronous machines such as power generators (hereinafter referred to as asynchronous machines) may also be included in the power control target.

FIG. 1 is a configuration diagram of a conventional online pre-calculation type power system stabilization system SS. The power system stabilization system SS includes, for example, a central processing unit 9, a central control unit 10, an accident detection terminal device 11, and a control terminal device 12.

Note that the central processing unit 9 may be referred to as a "central processing unit (pre-processing unit)," and in that case, the central processing unit 10 may be referred to as a "central processing unit (post-processing unit)." There is. Note that the central processing unit 9 and the central control unit 10 may be configured as one device by integrating their respective functions (for example, Patent Document 1).

FIG. 2 is a configuration diagram of a power system E in which a power system stabilization system SS is installed. For example, in addition to the power system stabilization system SS described above, the power system E further includes a generator 1, a bus bar 2, a power transmission line or transformer 3, a circuit breaker (CB) 4, and a current measuring device (CT). ) 5, a voltage measuring device (VT) 6, and an accident elimination relay system 7.

The central processing unit 9, the central control unit 10, the accident detection terminal device 11, and the control terminal device 12, which are the components of the power system stabilization system SS, are connected by communication equipment 8 (for example, a signal line, a communication device, etc.). Ru. The accident detection terminal device 11 is installed at, for example, a substation. Further, the control terminal device 12 is installed at, for example, a power plant. The central control device 10 is installed at a location where it can communicate with other devices, and may be installed at the same location as the accident detection terminal device 11 and the control terminal device 12. Further, the central control device 10 may be configured to include the functions of the accident detection terminal device 11 and the control terminal device 12. The central processing unit 9 is installed at a location connectable to the power supply information network N, such as a central power supply control center, so that system information can be obtained online.

The central processing unit 9, the central control unit 10, the accident detection terminal device 11, and the control terminal device 12 that constitute the power system stabilization system SS are configured by, for example, a processor (hardware) such as a CPU (Central Processing Unit). This is realized by executing a program (software). In addition, some or all of these components may include hardware such as LSI (Large Scale Integrated circuit), ASIC (Application Specific Integrated Circuit), FPGA (Field-Programmable Gate Array), and GPU (Graphics Processing Unit). It may be realized by a circuit unit (including circuitry), or it may be realized by cooperation of software and hardware. The program may be stored in advance in a storage device (a storage device equipped with a non-transitory storage medium) such as an HDD (Hard Disk Drive) or flash memory, or may be stored in a removable storage device such as a DVD or CD-ROM. It is stored in a medium (non-transitory storage medium), and may be installed in the storage device 150 or the storage device 160 by attaching the storage medium to a drive device. The storage device 150 and the storage device 160 are configured of, for example, an HDD (Hard Disk Drive), a flash memory, an EEPROM (Electrically Erasable Programmable Read Only Memory), a ROM (Read Only Memory), or a RAM (Random Access Memory). .

The central processing unit 9 includes, for example, a system information collection means 101, a system model creation means 102, an analysis condition setting means 103, a stability determination means 104, an electrical control target selection means 105, and a storage device 150. . The storage device 150 stores, for example, programs executed in the central processing unit 9, system equipment data 151, hypothetical accident data 152, electricity control candidate data 153, and a control table 154.

The system information collecting means 101 collects system information (online data for power supply) input from the power system E via the power supply information network N. The system equipment data 151 includes information such as the impedance of various equipment such as generators, power transmission lines, and transformers that make up the power system E, for example. The system information is, for example, the connection state of the power system E that can be determined by the on/off state of the circuit breaker (CB) 4, or the amount of electricity information measured by the current meter (CT) 5 or voltage meter (VT) 6. This is information about the power supply and demand status and power flow status that can be grasped. System information provided from the power supply information network N is collected by the system information collection means 101 at a fixed cycle or at a system information update cycle. The system information collection means 101 outputs the collected system information to the system model creation means 102.

The system model creation means 102, for example, based on the system information inputted from the system information collection means 101 and the system equipment data 151, performs the current process in a series of processes repeatedly executed at a predetermined period by the central processing unit 9, which will be described later. Create an analytical system model that represents the system status at the processing timing. System model creation means 102 outputs the created analytical system model to analysis condition setting means 103.

The analysis condition setting unit 103 includes, for example, a system model acquisition section 103a and an analysis condition setting section 103b. The system model acquisition unit 103a acquires the analysis system model created by the system model creation means 102. The analysis condition setting unit 103b uses the system model for analysis acquired by the system model acquisition unit 103a and the assumed accident data 152 (see FIG. 5) that stores definitions related to assumed accidents. Set analysis conditions based on type data. The analysis conditions include, for example, information on combinations of electric control targets to be controlled when a hypothetical accident occurs. The hypothetical accident includes, for example, information indicating a monitoring point (for example, a power transmission line, etc.) for monitoring an accident and the nature of the accident. The analysis condition setting section 103b outputs the set analysis conditions to the stability determining means 104. A monitoring point is a power system facility that monitors the occurrence of a system fault, and is sometimes called a fault point.

The stability determining unit 104 performs transient stability calculation based on the analysis conditions output from the analysis condition setting unit 103b.

The stability determination unit 104 includes, for example, an analysis condition acquisition unit 104a, a transient stability calculation unit 104b, and a stability determination unit 104c.

The analysis condition acquisition section 104a acquires the analysis conditions set by the analysis condition setting means 103. The transient stability calculation unit 104b performs transient stability calculation to simulate the behavior of the power system when a hypothetical accident set in the analysis conditions occurs, based on the analysis conditions acquired by the analysis condition acquisition unit 104a. Based on the result of the transient stability calculation obtained by the transient stability calculation unit 104b, the stability determination unit 104c stabilizes the power system without causing the generator parallel to the power system to step out under the analysis conditions. Determine whether or not it can be operated. The stability determination unit 104c determines that the system is unstable if there is a generator that steps out of synchronization, and determines that the system is stable if all the generators can maintain synchronized operation. The stability determination unit 104c outputs the result of the transient stability calculation and the determination result regarding the synchronization stability to the electrical control target selection unit 105. In FIG. 1, the result of the transient stability calculation and the determination result regarding synchronization stability are shown together as a "stability determination result."

The electricity restriction target selection unit 105 includes, for example, an electricity restriction object selection unit 105a and a control table setting unit 105b.

The power control target selection unit 105a selects a generator to be controlled when the determination result regarding synchronous stability outputted by the stability determination unit 104c is unstable. The power restriction target selection unit 105a selects a generator to be controlled from among the generators set in the power restriction candidate data 153. For example, the electricity shedding target selection unit 105a determines, with respect to the generator set in the electricity shedding candidate data 153, using the result of the transient stability calculation output by the stability determining unit 104c, when the generator is subjected to electricity shedding. An index representing the stabilization effect is calculated, and a generator to be subjected to power shedding is selected based on the stabilization effect index. The control table setting unit 105b sets, in the control table 154, the combination of electrical restriction targets for each hypothetical accident selected by the electrical restriction target selection unit 105a. Further, the control table setting unit 105b transmits the set control table 154 to the central control device 10.

Note that the above-described series of processing by the central processing unit 9 is repeatedly performed at a predetermined period. The predetermined period is, for example, the time (for example, 30 seconds) in which updating of the control table is completed for all assumed accidents. Further, the predetermined period may be set by the administrator of the power system stabilization system SS based on the scale of the power system E, the number of assumed accidents, and the processing capacity of the central processing unit 9.

The central control device 10 includes, for example, an electrical control target determining means 106 and a storage device 160. The storage device 160 stores, for example, programs executed in the central control device 10, a control table 161, and the like.

The electricity restriction target determining unit 106 includes, for example, a control table acquisition unit 106a and a verification processing unit 106b.

The control table acquisition unit 106a receives the control table 154 transmitted by the central processing unit 9, and stores it in the storage device 160 as the control table 161. When the verification processing unit 106b acquires information regarding the accident type of the electric power system E from the accident detection terminal device 11, which will be described later, the verification processing unit 106b collates the combination of electrical control targets in the hypothetical accident associated with the accident type with the control table 161. The acquired combination of power restriction targets is determined as an actual power restriction target, and a power restriction command is transmitted to the control terminal device 12 that controls the power restriction targets.

The accident detection terminal device 11 includes, for example, accident type detection means 107. The accident type detection means 107 acquires system information from the power system E, detects the occurrence of a system fault in the power system E, and further determines the type of fault when a system fault is detected. When the accident detection terminal device 11 detects the occurrence of a system accident, it determines the accident type and transmits it to the central control device 10.

The control terminal device 12 includes, for example, a control means 108. The control means 108 transmits a cutoff command to the target electrical control target based on the electrical control command received from the central control device 10 .

FIG. 3 is a flowchart showing an example of processing by the central processing unit 9. The process of the flowchart shown in FIG. 3 is repeatedly executed at a predetermined period.

First, the system information collecting means 101 collects system information of the power system E via the power supply information network N (step S1). Next, the system model creation means 102 performs state estimation calculations, system reduction, etc. based on the collected system information and system equipment data 151, and creates an analysis system model of the power system E (step S2).

Next, the analysis condition setting means 103 sets analysis conditions based on the analysis system model created in step S2 and the assumed accident data 152 (step S3). Next, the stability determining means 104 performs a transient stability calculation of the analysis conditions set in step S3 (step S4).

Next, based on the result of the transient stability calculation in step S4, the stability determining means 104 determines whether all the synchronous machines connected to the power system E will operate stably without stepping out if a hypothetical accident occurs. It is determined whether or not it can be maintained (step S5). In step S5, the stability determining means 104 determines that the synchronous stability is stable if the synchronous machine does not step out of synchronization, and determines that the synchronous stability is unstable if the synchronous machine loses synchronization.

FIG. 4 is a diagram showing an example of a transient stability calculation result. Figure 4 shows the output P _e of the generator connected to the power grid and the phase angle difference when a hypothetical accident occurs at time t _F , the accident is removed at time t _C , and power cuts are implemented at time t _GS . δ and a simulation waveform of frequency f. Note that the phase angle difference δ is the difference between the internal phase angles of the reference generator and the generator. The time at which each event occurs is determined by the operating time of the fault elimination relay system and circuit breakers, etc., for example _, approximately 60 milliseconds, and time t _GS is determined by the operating time of the fault elimination relay system and circuit _breakers , etc. It is determined by the operating time of the stabilization system, circuit breaker, etc., and is, for example, about 200 milliseconds. As in this example, when the result is that the synchronous operation of the generators is maintained without the phase angle difference δ diverging, it is determined in step S5 that the synchronous stability is stable.

If it is not determined that the power is stable in step S5, the electrical power reduction target selection means 105 selects a generator (synchronous machine) to be electrically controlled when the assumed accident occurs from the electrical power reduction candidate data 153. The electrical control target is added and the process returns to step S3 (step S6). In this case, in step S3, the analysis condition setting means 103 sets analysis conditions including conditions for electrically controlling the electrically controlled object selected in step S6.

When it is determined that the vehicle is stable in step S5, the electrical control target selection means 105 determines whether or not stability determinations for all hypothetical accidents have been completed (step S7). If it is determined that the stability determinations for all hypothetical accidents have not been completed, the electrical control target selection means 105 returns the process to step S3 and performs the stability determination for the next hypothetical accident. If it is determined that the stability determination for all hypothetical accidents has been completed, the electric control target selection means 105 sets the control table 154 (step S8), and ends the process of this flowchart.

FIG. 5 is a diagram showing an example of contents included in the assumed accident data 152. _NF in the figure is the number of assumed accidents and is a natural number. The hypothetical accident data 152 includes, for example, information such as a hypothetical accident number for identifying hypothetical accidents, monitoring points, and accident aspects detected at the monitoring points. Information such as "3Φ6LG-O" in the diagram is a code representing the accident mode. The combination of monitoring points and accident aspects is called an accident type. The analysis condition setting unit 103b sets, for example, the combination of the analysis system model acquired by the system model acquisition unit 103a, the assumed accident included in the assumed accident data 152, and the electric power restriction target selected by the electric power restriction target selection means 105. Set the analysis conditions using .

FIG. 6 is a flowchart illustrating an example of the process of the power restriction target selection unit 105a that selects power restriction targets based on an index representing a stabilizing effect. The process in the flowchart of FIG. 6 corresponds to step S6 in the flowchart shown in FIG.

First, the power restriction target selection unit 105a selects power restriction candidates based on power restriction candidate data 153 that records generators that can be controlled by the power system stabilization system SS, that is, generators in which the control terminal device 12 is installed. (Step S601).

FIG. 7 is a diagram showing an example of the electric bill candidate data 153. _NGA in the figure is the number of power restriction candidate generators and is a natural number. The power system candidate data 153 includes information such as, for example, a power system candidate number for identifying a power system candidate generator, a power source name, and a type of power source. The electricity control candidate data 153 may be provided for each assumed accident monitoring point.

The electric power restriction target selection unit 105a first determines that the generator is unstable from among the generators _NGA set in the electric power restriction candidate data 153 using the determination condition of formula (1) or formula (2). The generator _NGS unit that is determined to be unstable within a certain period of time from the time when the generator is set is selected as a power control candidate. That is, the power restriction target selection unit 105a excludes power restriction candidate generators that do not satisfy the determination conditions from the power restriction candidates. N _GS is a natural number, and the relationship is N _GS ≦N _GA .

{δ _i(t) −δ _S(t) }≧δ _k ...(1)

{δ _i(t) -δ _S(t) }≧δ _k and {ω _i(t) -ω _S(t) }≧ω _k ...(2)

Here, δ _i(t) is the internal phase angle of the generator in power system E at time t, ω _i(t) is the angular velocity of the generator in power system E at time t, and δ _S(t) is the time The internal phase angle of the reference generator at time t, ω _S(t) is the angular velocity of the reference generator at time t, i is the generator number (i = 1 to N _GA ), t is the simulation time in the transient stability calculation, δ _k and ω _k are thresholds.

After the processing in step S601, the power restriction target selection unit 105a calculates the acceleration energy as a stabilization effect index AE for the generator _NGS selected as a power restriction candidate (step S602), and calculates the operational constraints of the power system E. The stabilization effect index AE is corrected using a weighting coefficient that takes into account (step S603), and the generator with the maximum stabilization effect index AE is selected as the power control target to be added (step S604).

FIG. 8 is a diagram showing an example of the results of calculating the stabilization effect index AE of the power restriction candidate using the transient stability calculation results. As shown in the figure, for example, information such as internal phase angle difference, angular velocity difference, and stabilization effect index of each power control candidate generator is included. The power restriction target selection unit 105a selects a generator with a large stabilization effect index AE as a power restriction target.

The above is the process of the power cut target selection unit 105a in the conventional power system stabilization system SS. The control table setting unit 105b sets the electricity control target selected by the electricity control target selection unit 105a in the control table.

Note that the power cut targets selected in step S6 are not limited to synchronous machines such as thermal power generators and nuclear power generators, but also asynchronous machines such as solar power generation and wind power generation that are renewable energy power sources (hereinafter referred to as renewable energy power sources). Machines may be included. When an asynchronous machine is to be subjected to electrical control, for example, methods for selecting electrical control targets described in Patent Document 2 and Non-Patent Document 2 can be applied. Patent Document 2 proposes a power system stabilization system that prioritizes renewable energy power sources over synchronous machines and performs power cuts. Non-Patent Document 2 describes a study on a method for selecting a renewable energy power source to be curtailed in a grid stabilization system that targets renewable energy power sources.

FIG. 9 is a diagram showing an example of contents included in the control table 154. The control table 154 includes information such as a hypothetical accident number and the electrical restriction target selected by the electrical restriction target selection means 105, for example.

For example, in the control table 154 shown in FIG. 9, if an accident with the assumed accident number "1" occurs, that is, a 3Φ6LG-O accident on the X transmission line of the A substation shown in FIG. 5, the control table 154 shown in FIG. Among the generators 1, generators SG1 and SG2 are to be electrically energized, and in the case of an accident with an assumed accident number of "2", it is stipulated that generator SG1 is to be electrically energized.

In this way, in the conventional power system stabilization system SS, by controlling some of the generators, the other generators are prevented from losing synchronization, and the synchronization stability of the power system is maintained. The generators that are subject to power regulation are mainly synchronous machines such as thermal power generation and nuclear power generation, and there are few grid stabilization system SS that target asynchronous machines such as solar power generation and wind power generation.

The reason why conventional power system stabilization systems SS mainly target synchronous machines is that asynchronous machines such as solar power generation and wind power generation have a lower output per power source than synchronous machines such as thermal power generation and nuclear power generation. is small, so it is necessary to electrically control many asynchronous machines in order to prevent synchronized machines from losing synchronization, and it is necessary to electrically control a synchronous machine that loses synchronization rather than electrically controlling the renewable energy power source of an asynchronous machine that does not lose synchronization. One possible explanation is that it is easier to understand the reason why the person was selected as the subject of the electric control.

It is expected that the introduction of asynchronous renewable energy power sources such as solar power generation and wind power generation will increase in the future. A power system with a large proportion of asynchronous machines in the power supply connected to the power system (hereinafter referred to as the asynchronous machine ratio) has a higher rate of motion stored in rotating machines connected to the power system than a power system with a small asynchronous machine ratio. Since the energy (hereinafter referred to as inertia) is small, the speed at which the frequency changes when the balance between power demand and supply is disrupted, the so-called rate of change of frequency (RoCoF), increases.

In a power system with a large proportion of asynchronous machines, when synchronous machines such as thermal power generators are electrified using the power system stabilization system SS, the inertia is further reduced. When a disconnection accident (hereinafter referred to as a power supply disconnection accident) occurs, the frequency rapidly decreases, and if the frequency drops to a level where the generator protection device operates, the generator protection device operates and many generators are chained together. may fall off, leading to a blackout.

Patent No. 5591505 Patent No. 6223833

Institute of Electrical Engineers of Japan Technical Report No. 801, "Relay technology to prevent system loss and accident spread", p74, p75, p88, p89, p91, p92, Institute of Electrical Engineers of Japan, October 2000 Shimo et al., “Study of system stabilization control method to limit renewable energy power sources”, Institute of Electrical Engineers of Japan Electric Power Technology/Power System Technology Joint Study Group, PE-19-071/PSE-19-083, September 2019 “Essential Reliability Services Whitepaper on Sufficiency Guidelines”, NERC, December. 2016, p1-2, https://www.nerc.com/comm/Other/essntlrlbltysrvcstskfrcDL/ERSWG_Sufficiency_Guideline_Report.pdf

The problem to be solved by the present invention is to provide a power system stabilization system that selects a target for power outage in which generators will not be chained down even if a power outage accident occurs in the power system after power outage has been implemented. It is.

The power system stabilization system of the embodiment includes a central processing unit, an accident detection terminal device, a central control device, and a control terminal device. The power source where the control terminal device is installed includes a synchronous power plant including thermal power generation, and an asynchronous renewable energy power source site including at least one of solar power generation and wind power generation. In addition, when selecting a power outage target, the central processing unit also performs transient stabilization based on current system information to ensure that even if a power outage accident occurs in the power system after power outage is implemented, a chain reaction of power outages will not occur. If a chain drop of power supplies occurs, the synchronous machine selected as the target for electrical control is removed, and an asynchronous machine is selected as the target for electrical control instead.

A power system stabilization system according to another embodiment includes a central processing unit, an accident detection terminal device, a central control device, and a control terminal device. The power source where the control terminal device is installed includes a synchronous power plant including thermal power generation, and an asynchronous renewable energy power source site including at least one of solar power generation and wind power generation. In addition, when selecting a power grid target, the central processing unit selects the power grid target so that the inertia of the power system does not fall below an inertia lower limit value determined and set in advance through offline power system analysis, If the inertia is below the inertia lower limit value, the synchronous machine selected as the electrical control target is removed, and an asynchronous machine is selected as the electrical control target instead.

FIG. 1 is a configuration diagram of a conventional online pre-calculation type power system stabilization system SS. FIG. 2 is a configuration diagram of a power system E in which a conventional power system stabilization system SS is installed. 5 is a flowchart showing an example of processing by a conventional central processing unit 9. The figure which shows an example of a transient stability calculation result. A diagram showing an example of assumed accident data 152. The flowchart which shows an example of the process by the conventional electrical control target selection part 105a. FIG. 3 is a diagram illustrating an example of conventional electricity control candidate data 153. FIG. 3 is a diagram showing an example of calculation contents of a conventional stabilization effect index. FIG. 3 is a diagram showing an example of a control table 154. FIG. 1 is a configuration diagram of a power system E in which a power system stabilization system SSA according to a first embodiment is installed. FIG. 3 is a diagram showing an example of electricity control candidate data 153 according to the first embodiment. 5 is a flowchart showing an example of processing by the central processing unit 9 according to the first embodiment. FIG. 3 is a diagram showing an example of analysis conditions according to the first embodiment. FIG. 3 is a diagram showing an example of a transient stability calculation result according to the first embodiment. FIG. 3 is a diagram showing an example of a frequency simulation waveform according to the first embodiment. FIG. 7 is a diagram showing an example of a frequency simulation waveform according to the second embodiment. 7 is a flowchart showing an example of processing by the central processing unit 9 according to the second embodiment. FIG. 7 is a diagram showing an example of conditions and results of offline power system analysis according to the second embodiment. FIG. 7 is a diagram showing an example of the results of offline power system analysis according to the second embodiment.

Hereinafter, a power system stabilization system according to an embodiment will be described with reference to the drawings.

(First embodiment)
The power system stabilization system SSA of the first embodiment will be described.

The central processing unit 9 of the electric power system stabilization system SSA of the first embodiment, when selecting the target of electric power restriction, prevents generators from being chained and disconnected even if a power failure accident occurs in the electric power system after the electric power restriction is implemented. Confirm this using transient stability calculation.

Hereinafter, specific processing of the central processing unit 9 will be explained with reference to FIGS. 10, 11, 12, 13, 14, and 15. In addition, in the following explanation, parts having the same functions as the conventional power system stabilization system SS explained in the background art will be given the same names and symbols, and specific explanations regarding the functions will be omitted. do.

FIG. 10 is a configuration diagram of a power system E in which the power system stabilization system SSA of the first embodiment is installed. Compared to the conventional power system stabilization system SS shown in FIG. The difference is that it is also installed at a renewable energy power source site including power generation equipment 22. Compared to the conventional power system stabilization system SS shown in Fig. 1, the processing configuration of the power system stabilization system SSA is different from the conventional power system stabilization system SS shown in Figure 1 because it targets renewable energy power sources (asynchronous machines) in addition to generators (synchronous machines). The contents of the system candidate data 153 and the processing of the central processing unit 9 are different.

Therefore, the following description will focus on the processing of the central processing unit 9 of the power system stabilization system SSA, which targets asynchronous machines in addition to synchronous machines.

FIG. 11 is a diagram illustrating an example of power restriction candidate data 153 in which the power system stabilization system SSA records power sources that can be subjected to power restriction, that is, power sources of power restriction candidates including an asynchronous machine in which the control terminal device 12 is installed. . The electricity control candidate data 153 may be provided for each assumed accident monitoring point. The power restriction target selection unit 105a of the power system stabilization system SSA selects a power restriction target from power source _NGA units that are power restriction candidates including the asynchronous machine set in the power restriction candidate data 153.

FIG. 12 is a flowchart showing an example of processing by the central processing unit 9. The processing in the flowchart of FIG. 12 differs from the flowchart showing the processing of the conventional power system stabilization system SS shown in FIG. 3 in that steps S101 to S108 are added. As shown in FIG. 12, the central processing unit 9 selects the electrical control target for the hypothetical accident through a series of processes in steps S1 to S6, and after determining that it is stable in step S5, the analysis condition setting means 103 selects the electrical control target for the assumed accident. The accident is added to the analysis conditions (step S101). Next, the stability determining means 104 performs transient stability calculation based on the analysis conditions set in step S101 (step S102).

FIG. 13 is a diagram showing an example of the analysis conditions set in step S101. Fig. 13 shows an example of an accident with the assumed accident number "1" shown in Fig. ₅ , where the assumed accident ( _A substation A substation X transmission line 3Φ6LO), power cutoff of generators SG1 and SG2 is implemented at time t _GS , and conditions are set for a power outage accident to occur at time t _GD . For example, a power supply failure accident sets the most severe accident condition imaginable in the current system state. Specifically, the power failure accident is set as the failure of all generators at the power plant with the highest output among the power plants connected to the power grid. The timing t _GD at which the power supply failure accident occurs is set to the timing when the power fluctuations caused by the assumed accident and the power outage have sufficiently converged, and if t _F is taken as the starting point (0 seconds), it is set to, for example, about 10 seconds. The timing t _GD may be set by referring to the transient stability calculation result in step S4 and confirming the timing at which the power fluctuation converges within a certain range.

FIG. 14 is a diagram showing an example of the results of the transient stability calculation performed in step S102. After the power failure accident occurred at time t _GD , the frequency f has decreased. The rate at which the frequency f decreases at this time is called the rate of change of frequency (hereinafter referred to as RoCoF).

FIG. 15 is a diagram showing the relationship between RoCoF and frequency fluctuation. As in the unstable case shown in FIG. 15, in a power system with small inertia, RoCoF is large and the frequency f rapidly decreases. If the frequency f drops to the level f _UFR at which the generator protection device operates, a large number of generators will drop out due to the operation of the protection device, and the frequency f will further decrease, eventually leading to a blackout. There is.

Therefore, in the processing by the central processing unit 9 according to the first embodiment, the stability determining means 104 determines that even if a power supply disconnection accident occurs, the frequency f is determined by the generator protection device, as in the stable case shown in FIG. It is confirmed that the operation level f does not fall to _UFR and that it recovers (step S103). This confirmation may be performed by confirming that the frequency f has not decreased to the operating level f _UFR of the generator protection device after a predetermined time, or by confirming that the frequency f has decreased to the lowest level, and then This may be done by confirming that the patient has recovered. In step S103, the stability determining means 104 determines that if the frequency f does not fall to the operating level f _UFR of the generator protection device, there is no abnormal frequency decrease, and if the frequency f falls below the operating level f _UFR of the generator protection device, there is an abnormal frequency decrease. , it is determined.

If it is determined in step S103 that there is an abnormal frequency drop, the power restriction target selection means 105 excludes the last selected synchronous machine from the power restriction target (step S104), and selects an asynchronous machine as a new power restriction target. (Step S105). The process of selecting an asynchronous machine as a target for power cut in step S105 is, for example, selection of a target for power cut in a power system stabilization system that targets a renewable energy power source (asynchronous machine) as a target for power cut, as described in Non-Patent Document 2. method can be applied.

Next, the analysis condition setting means 103 sets analysis conditions including conditions for electrically controlling the electrically controlled object selected in step S105 (step S106).

Next, the stability determining means 104 performs a transient stability calculation based on the analysis conditions set in step S106 (step S107), and determines synchronous stability based on the result of the transient stability calculation in step S107 ( Step S108). If it is determined in step S108 that the stability is stable, the stability determining means 104 returns the process to step S101.

If it is determined in step S108 that the stability is unstable, the stability determining means 104 returns the process to step S105. In this case, the power restriction target selection unit 105 additionally selects an asynchronous machine as a power restriction target in step S105, and repeats the process until the determination of synchronous stability becomes stable in step S108.

If it is determined in step S103 that there is no abnormal frequency drop, the electrical control target selection means 105 determines whether stability determinations for all hypothetical accidents have been completed (step S7). If it is determined that the stability determinations for all hypothetical accidents have not been completed, the electrical control target selection means 105 returns the process to step S3 and performs the stability determination for the next hypothetical accident. If it is determined that the stability determinations for all hypothetical accidents have been completed, the electrical control target selection means 105 sets the control table 154 (step S8), and ends the processing of this flowchart.

As explained above, in the power system stabilization system of the first embodiment, even if a power failure accident occurs in the power system after power outage is implemented, it is possible to select a power outage target that will not cause a chain reaction of power outages. can. In addition, the power system stabilization system of the first embodiment performs transient stability calculations based on online system information to confirm that chain dropouts of power supplies do not occur. It is possible to select the target, and there is no restriction such as leaving an excessive number of synchronous machines.

(Second embodiment)
Next, a power system stabilization system SSB according to a second embodiment will be described.

When the central processing unit 9 of the power system stabilization system SSB of the second embodiment selects the electrical power control target, it selects the electrical power control target so as to leave a certain inertia.

Hereinafter, specific processing of the central processing unit 9 will be explained with reference to FIGS. 16, 17, 18, and 19. In the following description, parts having similar functions to those described in the prior art or the first embodiment will be given the same names and numerals, and specific descriptions of the functions will be omitted. .

FIG. 16 is a diagram showing an example of a frequency simulation waveform according to the second embodiment. FIG. 16 is a diagram showing the relationship between the magnitude of inertia and frequency fluctuation, which was obtained by performing a power system analysis on a desk (offline) in advance. As shown in the unstable case shown in Figure 16, a power system with a large asynchronous machine ratio has a small inertia, so the RoCoF after a power supply failure occurs is large, and the frequency f falls below the operating level f _UFR of generator protection, resulting in a black state. There is a risk of going out. On the other hand, as in the stable case shown in FIG. 16, a power system with a small asynchronous machine ratio has a large inertia, so the RoCoF is small and abnormal frequency drops are unlikely to occur.

Since there is such a relationship between the asynchronous machine rate and frequency fluctuation, the central processing unit 9 of the power system stabilization system SSB uses the inertia (hereinafter referred to as SIR) when selecting the target of power control. The electrical control target is selected so that the inertia (abbreviation for "Response") does not become smaller than a predetermined inertia (hereinafter referred to as "SIR lower limit value").

FIG. 17 is a flowchart showing an example of processing by the central processing unit 9. The processing in the flowchart of FIG. 17 differs from the flowchart showing the processing of the conventional power system stabilization system SS shown in FIG. 3 in that step S201 and steps S104 to S108 are added. As shown in FIG. 17, the central processing unit 9 selects the electrical control target for the assumed accident through a series of processes from steps S1 to S6, and after determining that it is stable in step S5, the electrical control target selection means 105 selects the electrical control target by the formula Using the conditional expression shown in (3), it is confirmed that the SIR is larger than the SIR lower limit value (step 201). The SIR is obtained, for example, using equation (4).

SIR > SIR lower limit value...(3)

SIR = Σ(H _i・P _MVAi ), i=1~ _NG ...(4)

Here, SIR is the total sum of kinetic energy [MVA seconds] stored in the synchronous machines connected to the power grid, H _i is the unit inertia constant of the synchronous machine i [seconds], and P _MVA is the unit inertia constant of the synchronous machine i The installed capacity [MVA] of _NG is the number of interconnected synchronous machines. An explanation regarding equation (4) is given in, for example, Non-Patent Document 3. The SIR lower limit value is determined by off-line power system analysis and is set in advance in the storage device 150 of the central processing unit 9.

Note that the SIR lower limit value differs for each power system depending on, for example, the characteristics of the power system and the number of synchronous machines connected to the power system. The SIR lower limit value is set in advance to a value that is strict with respect to the conditional expression shown in equation (3), that is, a large value that increases the tendency for it to be determined that the condition of equation (3) is not satisfied in step S201. You can leave it there. The SIR lower limit value is, for example, the ratio (ratio) to the maximum value of SIR when no electricity is cut off, or in other words, the ratio to SIR under the condition that all synchronous machines that can be connected to the power grid are connected. You can also set it with

FIG. 18 is a diagram showing an example of the conditions and results of offline power system analysis when determining the SIR lower limit value. In offline power system analysis, we use a system model for analysis of various assumed system conditions, such as the magnitude of power demand and the operating status of generators (operating synchronous machines and their output, spinning reserve, and asynchronous machines). Analytical system models are created for multiple power systems with different power generation conditions (power generation status), and transient stability calculations are performed for each analytical system model simulating a power supply disconnection accident. Analytical system models for a plurality of power systems may include models with different temporal elements, such as seasons and time zones, for example. In the example shown in Fig. 18, the frequency f after a power supply failure is determined to be the operating level for generator protection based on the SIR for N _S system conditions (system model for analysis) and the transient stability calculation results at the time of a power supply failure. The result of determining whether or not the value is below f _UFR using equation (5) is recorded. The determination result of the frequency f is "OK" when the condition of equation (5) is satisfied, and "NG" when the condition is not satisfied.

f > f _UFR ...(5)

FIG. 19 is a diagram showing the distribution of the number of analytical system models based on the SIR value from the determination result of the frequency f shown in FIG. 18. A diagonal line square indicates an analysis system model with a determination result of "NG", and a white square indicates an analysis system model with a determination result of "OK". Generally, the larger the SIR of the analytical system model, the more likely the determination result will be "OK."

Using equation (6), among the SIRs of the analytical system models whose determination result is "NG", the one with the largest value is determined as SIR _{NG_max} .

SIR _{NG_max} = max(SIR _i )...(6)

Here, i is the number of the analytical system model for which the determination result is "NG".

Next, using equation (7), among the SIRs of the analysis system model for which the determination result is "OK", the smallest SIR whose value is larger than SIR _{NG_max} is selected as the SIR lower limit value.

SIR lower limit value = min(SIR _j )...(7)

Here, j is the number of the analytical system model for which the determination result is "OK" and the condition of equation (8) is satisfied.

SIR _j > SIR _{NG_max} ...(8)

If it is determined in step S201 that the condition of formula (3) is not satisfied, the power restriction target selection means 105 excludes the last selected synchronous machine from the power restriction target (step S104), and selects it as a new power restriction target. An asynchronous machine is selected (step S105).

Next, the analysis condition setting means 103 sets analysis conditions including conditions for electrically controlling the electrically controlled object selected in step S105 (step S106).

Next, the stability determining means 104 performs a transient stability calculation based on the analysis conditions set in step S106 (step S107), and determines synchronous stability based on the result of the transient stability calculation in step S107 ( Step S108). When it is determined in step S108 that the stability is stable, the stability determining means 104 returns the process to step S201.

If it is determined in step S108 that the stability is unstable, the stability determining means 104 returns the process to step S105. In this case, the power restriction target selection means 105 additionally selects an asynchronous machine as a power restriction target in step S105, and repeats the process until the determination of synchronous stability becomes stable in step S108.

If it is determined in step S201 that the condition of formula (3) is satisfied, the electrical control target selection means 105 determines whether stability determinations for all hypothetical accidents have been completed (step S7). If it is determined that the stability determinations for all hypothetical accidents have not been completed, the electrical control target selection means 105 returns the process to step S3 and performs the stability determination for the next hypothetical accident. If it is determined that the stability determinations for all hypothetical accidents have been completed, the electrical control target selection means 105 sets the control table 154 (step S8), and ends the processing of this flowchart.

As explained above, in the power system stabilization system of the second embodiment, even if a power supply failure accident occurs in the power system after power outage is implemented, it is possible to select a power outage target that will not cause a chain reaction of power outages. can. In addition, in the power system stabilization system of the second embodiment, the SIR lower limit value obtained through offline power system analysis is set in advance in the power system stabilization system, and the power system is configured to prevent the SIR from falling below the SIR lower limit value. Since the control target is selected, the power system stabilization system does not need to perform transient stability calculations that include power supply dropout accidents, so the increase in calculation load is small and the cost of the system can be suppressed.

Although several embodiments of the invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included within the scope and gist of the invention as well as within the scope of the invention described in the claims and its equivalents.

SS: Power system stabilization system, E: Power system, N: Power supply information network, 1: Generator (synchronous machine), 2: Bus bar, 3: Transmission line or transformer 4... Circuit breaker (CB), 5... Current measuring device (CT), 6... Voltage measuring device (VT), 7... Accident removal relay system, 8... Communication equipment, 9... Central processing unit, 10... Central control device, 11... Accident detection terminal device, 12... Control terminal device, 21... Solar power generation equipment, 22... Wind power generation equipment, 101... System information collection means, 102... System model creation means, 103... Analysis condition setting means, 104... Stability determination means, 105... Electric control target selection means, 106... Electric control target determining means, 107... Accident type detection means, 108... Control means

Claims (2)

Collect current system information and create a system model for analysis, perform transient stability calculations for multiple hypothetical accidents, select electrical control targets necessary to maintain synchronized stability of the power system, and set them in the control table. and a central processing unit that repeatedly transmits the control table to the central control unit;
an accident detection terminal device that determines an accident type when a system accident occurs and transmits information on the accident type to the central control device;
the central control unit that determines the electricity control target by comparing information on the accident type received from the accident detection terminal device with the control table received from the central processing unit, and transmits an electricity control command;
An electric power system stabilization system comprising: a control terminal device that disconnects the power source determined to be subject to electric power restriction from the electric power system according to the electric power restriction command received from the central control device,
The power source where the control terminal device is installed includes a synchronous machine power plant including thermal power generation, and an asynchronous machine renewable energy power source site including at least one of solar power generation and wind power generation,
When selecting the power outage target, the central processing unit performs transient stability based on current system information to ensure that even if a power outage accident occurs in the power system after power outage is implemented, a chain loss of power supplies will not occur. The present invention is characterized in that the synchronous machine selected to be the target of the electric power restriction is removed and an asynchronous machine is selected as the target of the electric power control in its place. Power grid stabilization system. Collect current system information and create a system model for analysis, perform transient stability calculations for multiple hypothetical accidents, select electrical control targets necessary to maintain synchronized stability of the power system, and set them in the control table. and a central processing unit that repeatedly transmits the control table to the central control unit;
an accident detection terminal device that determines an accident type when a system accident occurs and transmits information on the accident type to the central control device;
the central control unit that determines the electricity control target by comparing information on the accident type received from the accident detection terminal device with the control table received from the central processing unit, and transmits an electricity control command;
An electric power system stabilization system comprising: a control terminal device that disconnects the power source determined to be subject to electric power restriction from the electric power system according to the electric power restriction command received from the central control device,
The power source where the control terminal device is installed includes a synchronous machine power plant including thermal power generation, and an asynchronous machine renewable energy power source site including at least one of solar power generation and wind power generation,
When selecting the electrical power restriction target, the central processing unit selects the electrical power restriction target so that the inertia of the power system does not fall below an inertia lower limit value determined and set in advance through offline power system analysis; A power system stabilization system characterized in that, when the inertia is less than the inertia lower limit value, the synchronous machine selected as the target of power restriction is removed, and an asynchronous machine is selected as the target of power restriction instead.

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